6,268 research outputs found

    On the existence and evolution of a spanwise vortex in laminar shallow water dipoles

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    The present work investigates the existence and evolution of a spanwise vortex at the front of shallow dipolar vortices. The vortex dipoles are experimentally generated using a double flap apparatus. Particle image velocimetry measurements are performed in a horizontal plane and in the vertical symmetry plane of the flow. The dynamics of such vortical structures is investigated through a parametric study in which both the Reynolds number Re=U0D0/Μ∈[90,470] and the aspect ratio α = h/D0∈[0.075,0.7],associated with the shallowness of the flow, are varied, where U0 is the initial velocity of the vortex dipole, D0 is the initial diameter, h is the water depth, and v is the kinematic viscosity of the fluid. The present experiments confirm the numerical results obtained in a companion paper by Duran-Matute et al. [Phys. Fluids 22, 116606 (2010)], namely that the flow remains quasi parallel with negligible vertical motions below a critical value of the parameter α2Re. By contrast, for large values of α2Re and αâ‰Č0.6, a three-dimensional regime is observed in the shape of an intense spanwise vortex generated at the front of the dipole. The present study reveals that the early-time motion and dynamics of the spanwise vortex do not scale on the unique parameter α2Re but is strongly influenced by both the aspect ratio and the Reynolds number. A mechanism for the generation of the spanwise vortex is proposed. For α≳0.6, a third regime is observed, where the spanwise vortex is replaced by a vorticity tongu

    Towards a better understanding of the psychological processes explaining safety behaviors at work

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    If occupational safety has substantially improved over the last 100 years (Hofmann, Burke & Zohar, 2017), it still remains a major concern for companies targeting to reduce the number of accidents to zero. Since the end of the 1980s, a way for improving workplace safety has been to apply the general management principles to safety, and to consider the influence of psychosocial and socio-organizational factors on safety as well as the importance of safety climate to promote in companies. These aspects characterize what Hale & Hovden (1998) termed the “third age of safety”. Chmiel & Hansez (2016) noted that “many job-related organizational phenomena may invoke multiple psychological processes that bear on safety behaviors and hence accidents” (p.133). Hence, besides the study of the direct impact of such psychosocial and socio-organizational factors on safety, the time has come to investigate more precisely which processes influence which types of safety outcomes. The aim of the present dissertation is therefore to examine task-related and contextual safety behaviors in the context of high risk industries and to investigate the psychological processes leading workers to adopt or not such behavior

    CLIC: An Agent-Based Interactive and Autonomous Piece of Art

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    International audienceThis work consists of integrating programming paradigms such as multi-agent systems and rule-based reasoning into a multimedia creation and display platform for interactive artistic creation. It has been developed in order to allow artists to build dynamic and interactive exhibitions based on pictures and sounds and featuring self-evolving and autonomous configurations

    READ : une plateforme pour l'évaluation de méthodes d'accÚs non-visuelles aux documents numériques

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    International audienceREAD (Restitution de l’Architecture des Documents)est un logiciel permettant un accĂšs non-visuel augmentĂ© Ă  des documents balisĂ©s. Cette plateforme a Ă©tĂ© initialement dĂ©veloppĂ©e pour Ă©valuer diffĂ©rentes mĂ©thodes de restitution de la mise en forme des textes [8]. La flexibilitĂ© de l’architecture de READ permet d’implĂ©menter facilement de nouvelles modalitĂ©s d’entrĂ©e et de sortie, ainsi que de nouvelles fonctionnalitĂ©s;l’application sera mise Ă  disposition prochainement en open source pour rĂ©utilisation non-commerciale. Le but principal est de permettre l’implĂ©mentation et l’évaluation rapide de mĂ©thodes d’accĂšs non-visuels aux documents, domaine dans lequel un effort de recherche certain est attendu [7]. Une dĂ©monstration permettra aux participants de la confĂ©rence d’observer les fonctionnalitĂ©s implĂ©mentĂ©es et d’avoir un aperçu des possibilitĂ©s d’extension de l’application

    Improving the accessibility of digital documents for visually impaired users : Contributions of the Textual Architecture Model

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    International audienceThis paper presents a framework which aims at describing text formatting, based on a model coming from the field of logic and linguistics, the Textual Architecture Model [23]. The goal is to improve documents accessibility for blind users. The project will later focus on evaluating the efficiency of different navigation and content presentation strategies, based on this framework

    Optimal nonlinear information processing capacity in delay-based reservoir computers

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    Reservoir computing is a recently introduced brain-inspired machine learning paradigm capable of excellent performances in the processing of empirical data. We focus in a particular kind of time-delay based reservoir computers that have been physically implemented using optical and electronic systems and have shown unprecedented data processing rates. Reservoir computing is well-known for the ease of the associated training scheme but also for the problematic sensitivity of its performance to architecture parameters. This article addresses the reservoir design problem, which remains the biggest challenge in the applicability of this information processing scheme. More specifically, we use the information available regarding the optimal reservoir working regimes to construct a functional link between the reservoir parameters and its performance. This function is used to explore various properties of the device and to choose the optimal reservoir architecture, thus replacing the tedious and time consuming parameter scannings used so far in the literature.Comment: 37 pages, 8 figure
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